Two-component heat developable diazotypes containing amidine compounds



United States Patent 3,389,995 TWO-COMPONENT HEAT DEVELOPABLE DIAZOTYPESCONTAINING AMID IN E COMPOUNDS Bert E. Tripp, Binghamton, Walter J.Welch, Port Dickinson, and Theodore Panasik, Vestal, N.Y., assignors toGeneral Aniline & Film Corporation, New York, N.Y., a corporation ofDelaware No Drawing. Filed Sept. 15, 1964, Ser. No. 396,715 Claims. (Cl.96-91) ABSTRACT OF THE DISCLOSURE Two-component diazotype photoprintingmaterial, and a sensitizing composition for its preparation, comprisinga surface having thereon a light-sensitive layer containing an azocoupling component, a light-sensitive diazonium compound, an acidstabilizer and at least one amidine compound selected from the groupconsisting of acetamidine, propionamidine, butyramidine,dicyandiamidine, guanyl thiourea and salts thereof.

This invention relates to two-component diazotype photoprinting materialsusceptible to development on heating, wherein said light-sensitivetwo-component diazotype layer comprises an amidine compoundcharacterized by the formula wherein X is selected from the groupconsisting of methyl, ethyl, propyl, NH--CN, NHCONH and NH-CSNHTwo-component diazotype photoprinting material comprises a supportingsheet, such as paper or film, having in a surface coating or layer, anazo coupling component and a light-sensitive diazonium compoundstabilized against premature coupling by inclusion of an acidstabilizer. On exposure of such coating to actinic light under an opaquepattern on a translucent background the light-sensitive diazoniumcompound is destroyed in the light-struck areas and on subsequentexposure to an alkaline development medium, such as gaseous ammonia, theacid stabilizer is neutralized and the residual diazonium compoundcouples with the coupling component to form an azo dye image in theareas corresponding to the opaque portions of the original pattern.Photoprinting materials of this type have met with various objections,such as the inconvenience associated with alkaline development and theneed for special equipment to avoid obnoxious ammonia odors.

It has been proposed to include in a two-component light-sensitivediazotype layer of the aforesaid nature, one or more reagents having anacid to neutral reaction which, on heating, are converted or decomposedto yield an alkaline reacting compound. Diazotype photoprintingmaterials containing such reagents can be developed after exposure tolight under a pattern as mentioned above by heating at a temperaturecausing the aforesaid modification or decomposition. The alkalinereaction product thereby formed neutralizes the acid stabilizer andcauses image-wise coupling of the residual diazonium compound with theazo coupling component. Premature coupling of the diazonium compoundduring storage has tended to destroy the desired contrast in many cases.

Numerous attempts have been made in the prior art 3,389,995 PatentedJune 25, 1968 ice to obviate some of the problems associated with theseprocesses. Thus, it has been proposed to prepare and apply theindividual diazotype and coupling materials to photographic sheets insuch a manner that they will form azo dyes under heat alone. An exampleis contained in U.S.P. 2,418,623. This patent proposed to use abiguanidine salt of a diazo compound which would decompose under theinfluence of heat to yield ammonia as a developing agent. In U.S.P.2,178,771 separate layers were pro posed and development by use of steamwas suggested. Various other patents have suggested other processesinvolving heat.

A number of other prior art investigators have suggested that thediazonium salts and couplers might be developed by heat, provided theyare applied in separate layers or coatings, the application of theseparate coatin'gs to be such as to avoid premature reaction betweenthem. U.S.P. 3,046,128 discloses a typical heat developing two-componentdiazotype of this type wherein a lightsensitive diazonium layer isapplied to one side of a paper base and an alkali generating layer isapplied to the opposite side of the paper. The alkali generating layercontains materials having low vapor pressure at room temperature orslightly above room temperature and substantial vapor pressure attemperatures of about to 200 C. The alkaline material either breaks downand passes as a vapor through the paper or merely passes through thepaper without any chemical breakdown. Various materials such as urea,guanidine, alkyl substituted ureas, ammonium salts of weak acids,volatile organic bases (ethylenediamine) are suggested. While thismethod has certain advantages it is relatively diflicult to packageseveral sheets of this material without a reasonable chance of prematuredevelopment of the diazotype layer. FIGURE 3 of this patent disclosesthe use of a vapor barrier film as a top coat for the diazo layer. Thislayer tends to minimize this disadvantage. However this increases thecost of the final product unduly. Further, care must be exercised in thecoating operations to preclude premature coupling.

It has also been suggested in some instances that the alkaline materialbe physically separated in some manner and only brought together laterfor development purposes. U.S.P. 3,076,707 discloses forming anon-reactive crystalline complex of a basic material such as an amine,and a phenolic compound or urea. This crystalline complex is decomposedafter exposure of the diazotype material by the influence of heat.

The use of alkali generating agents, such as urea or trichloroaceticacid (sodium trichloroacetate in an acidic system) for coupling also hasbeen proposed in the prior art. A reaction would take place subsequentlyon heating. However, urea decomposes at moderate storage temperature andeven at normal room temperature. Furthermore, relatively large amountsof urea are required for satisfactory development. For example U.S.P.3,046,128 sug gests using up to 3,000 grams of urea per one thousandsquare feet of diazotype paper. It is difficult to store materials ofthis type and maintain proper quantities over moderate periods of time.The trichloroacetic acid sodium trichloroacetate system has not beensatisfactory, in general, because the excess trichloroacetic acidusually causes severe degeneration of the paper. In addition, the sodiumtrichloroacetate itself tends to cause the diazonium salt to decomposeprematurely,

Degeneration of cellulosic bases is not a problem peculiar to the use oftrichloroacetic acid heat development. All two-component diazotypespresent this problem with more or less severity. Decomposition is due tothe acidic nature of the materials used to prevent premature coupling.

The object of this invention is to provide a new source of alkalinegenerating material which can be included in a sensitized composition ofheat developable diazotype material. Anotherobject of this invention isto provide heat developable light-sensitive diazotype materialcontaining an alkali generating material which is stable for extendedperiods of storage. A further object is to provide twocomponentdiazotype materials which have a much smaller tendency to degrade thepaper base.

We have now found that the objects of our invention are accomplished byemploying an amidine compound characterized by the structure and saltsthereof as the alkali generating material. In the above formula Xrepresents methyl, propyl, ethyl,

Typical compounds of this class are acetamidine, propionamidine,butyramidine, dicyandiamide, dicyandiamidinc, guanyl thiourea, etc. Allof these compounds are used as salts except for dicyandiamide which isessentially neutral. Suitable salts include the hydrochloride,carbonate, sulfate, etc. The amidine compound can be added to thesensitizer as a salt or the salt formed in situ by adding suitable acid.

Diazotypes of this invention are unexpectedly stable. This is contraryto what one would expect from the disclosure of U.S.P. 3,046,128 wherethe basic material is applied to the opposite side of the sheet of paperbearing a heat-sensitive diazotype layer and U.S.P. 3,076,707 whichcomplexes tetramethylguanidine with 4,4-'butylidene-bis-(6-tertiarybutyl-rn-cresol). Further, the amidine compound acts as a stabilizerpreventing undue degradation of the paper base.

The quantity of amidine compound employed in accordance with thisinvention advantageously ranges from 1 to about 15% by weight of thediazotype sensitizing solution, and constitutes from about 3 to about40% by weight of the non-volatile components of the sensitizingcomposition and of the resultant light-sensitive layer. In general theamidine compound comprises from about 1 to 25 parts by weight per partby weight of diazonium compound. Best results have been obtained usingabout to parts of amidine compound per part by weight of diazoniumcompound.

The sensitizing compositions of this invention may contain aslight-sensitive stable diazonium compounds, those listed in U.S. Patent2,501,874 and in the article by Van der Grinten in Photographic Journal,volume 92 (B), page 46. They are especially diazonium compounds derivedfrom N-monoor N-di-substituted p-phenylenediamines, e.g., diazotizationproducts of:

N,N-dimethyl-p-phenylenediamine N,N-diethyl-p-phenylenediamineN-benzyl-N-ethyl-p-phenylenediamine N-ethyl-para-phenylenediamineN,N-diethyl-2-ethoxy-p-phenylenediamineN,N-'bis-hydroxyethyl-p-phenylenediamineN-ethyl-2-methyl-p-phenylenediamineN-beta-hydroxyethyl-Nnnethyl-p-phenylenediamine 4-morpholinophenylamineThese compounds are preferably stabilized in the form of their doublesalts with zinc chloride, tin chloride, cadmium chloride and the like.

A coupling components which can be incorporated in the materials of theinvention are for example:

2-(m-hydroxyphenoxy)ethanol 2,3-dihydroxynaphthalene1,8-dihydroxynaphthalene Phloroglucinol Resorcinol OctylresorcinalAlpha-resorcylamid 3-methyl-l-phenyl-S-pyrazolone AcetoacetanilideH-acid 2,3-dihydroxynaphthalene-o-sulfonic acid 2,5-xylenol Z-methylresorcinol Acid stabilizers such as citric acid, tartaric acid, boricacid, acetic acid and similar acid reacting compounds are used toprevent premature coupling of the diazonium salt and azo couplingcomponent.

In addition to the foregoing materials there can also be includedreagents commonly employed in diazotype photoprinting materials, as forexample, intensifiers such as ammonium sulfate, zinc chloride or nickelsulfate; stabilizing agents such as thiourea, a-thiosinamine',accelerators such as 1-allyl-3-beta-hydroxyethyl-thiourea orl-allyl-thiourea; hygroscopic agents such as glycol or glycerin; andwetting agents such as saponin, lauryl sulfate, keryl benzene sulfonateor oleyl-N-methyltaurine.

Moreover, there can be included, finely divided or colloidal silica oralumina, and/or aqueous dispersions of colloidal solutions of organicfilm-forming binders, such as colloidal water-soluble polyvinylalcohol,hydroxyethylcellulose, methylcellulose, gelatin or the like, orlatex-like dispersions of polyvinyl chloride-acetate, polyvinylenechloride, polyacrylonitrile or polymethylmethacrylate.

The components of the sensitizing composition are preferablyincorporated in a single solution or suspension, and applied in a singlecoating step to the base. The latter may be paper, or film such asregenerated cellulose, cellulose acetate or other plastic films.However, the various components of the sensitizing composition can beapplied, if desired, in two successive coatingone containing, forexample, the diazonium salt, and another the alkali generatingheat-sensitive reagent, the azo coupling component being incorporated ineither of the two layers.

The material coated in accordance with this invention is developed afterexposure under an opaque pattern on a translucent background, by heatingat temperatures between and 200 C., and preferably between 180 C., atwhich temperature the amidine compound is converted to an alkalinematerial. This promotes coupling of the residual diazonium compound withthe azo coupling component in the areas corresponding to the opaquepattern to form an azo dye image.

The following examples are merely illustrative and should not beconstrued as limiting the scope of this invention. In the examples thatfollow, parts and percent ages are by weight unless otherwise indicated.

EXAMPLE I A paper base was sensitized with the following heatdevelopingcomposition:

Parts by weight The paper was dried and exposed to light under atranslucent original. The exposed paper was developed by passing itthrough a heated chamber having temperatures of 121 to 177 C. A blue dyewas formed in the image areas of the heat-developed print. If theacetamidine compound is replaced by dicyandiamide, or a salt ofdicyandiamidine or guanyl thiourea, a like result is obtained. If theamidine compound is omitted from the sensitizing composition, no dyeimage of consequence results of the heat-developing coating.

EXAMPLE 'II A paper base was sensitized with the followingheatdeveloping composition:

Parts by weigh Citric acid 0.5 Sodium6,7-dihydroxynaphthalene-Z-sulfonate 2-methyl resorcinol ResorcinolMagnesium chloride Dicyandiamide 4 N,N dimethylaminobenzenediazoniumchlorozincate 0.6 Polyvinyl alcohol, fully hydrolyzed 4.0 Silica 4.0Polyvinyl acetate emulsion 5.0 Water 100.0

The base was dried and exposed to light under a translucent original.The exposed paper was developed by passing it through a heated chamberhaving temperatures of 121 to 177 C. A black dye image was formed in theimage areas of the print. Essentially the same results are obtained bysubstituting the amidine compounds of this invention for thedicyandiamidine. If no amidine compound is used there is little or nodye image formation upon development.

EXAMPLE HI A transparent, light-weight rag paper was sensitized with thefollowing heat-developing composition:

The paper was dried and exposed to light under a translucent original.The exposed paper was developed by passing it through a heated chamberhaving temperatures of 121 to 177 C. A brown sepia-like image was formedin the image areas of the heat-developed print and the actinic opacityof the image was adequate for use of the heat developed print as anintermediate for reprinting onto standard blue or blackline heatdeveloped papers. A formulation having no amidine compound yielded dyeimages that were very weak or non-existent.

EXAMPLE IV This example illustrates the improved strength of the paperbase when using an amidine compound of this invention in a sensitizingcomposition. The paper base material was coated uniformly with thefollowing sensitizing composition:

Parts of weight Citric acid 3.0 Sodium6,7-dihydroxynaphthalene-Z-sulfonate 4.0 Zinc chloride 7.0 Thiourea 5.04-dimethylamiuobenzenediazonium chlorozinate 2.0 Silica 5.0 Polyvinylacetate emulsion 5.0 Dicyandiamide 5.0 Water 10010 The same paper basematerial was coated with the same sensitizing composition having nodicyandiamide. The papers were dried to 3 /2% moisture and subjected toforced aging tests. The results are as follows where L stands for withthe grain and C for across the grain:

No Dicyandiamide Forced Aging Dicyandiamide Conditions Tear 54 190 5hours, 150 F.

14 171 72 hours, 120 F.

The above table illustrates that the amidine compounds of this inventioneffectively stabilize cellulosic paper base materials againstdegradation resulting from the acidic components and acidic saltcomponents of two-component diazotype printing materials. The abovecomposition can be used to prepare two-component heat-developingdiazotypes or the more conventional-two-component ammonia developingdiazotypes.

The amidine compounds of this invention can be advantageously used inconjunction with alkali metal salts of strong acids, which decomposableon heating. The decomposable alkali metal salts of strong acids tend toreinforce and sharpen the image provided by the amidine compounds. Ineffect the decomposable alkali metal salts of strong acids are theprimary developing agents while the amidine compounds act secondarily asdeveloping agents and primarily as stabilizers to prevent degradation ofthe cellulosic substrate. Suitable alkali metal salts of strong organicacids which are decomposed on heating to form basic compounds includealkali metal salts (e.g., Na, K) of malonic, oxalic, maleic or benzenesulphinic acids, alkali metal salts of aliphatic monocarboxy acids of 1to 3 carbon atoms having negative chain substituents such as halogen, ONor N0 in alpha or beta positions; and of these are preferred the alkalimetal (e.g., Na, K), ammonium and nitrogen base salts or trichloroaceticacid.

EXAMPLE V This example illustrates the use of dicyandiam'ide with analkali metal salt of a strong decomposable organic acid. A paper basewas sensitized with the following heat developing formulation:

Parts by weight 4 N,N-dimethylaminobenzenediazonium chlorozincate 0.6Dicyandiamide 5 Sodium trichloroacetate 4 Polyvinyl alcohol, fullyhydrolyzed 4 Silica 4 Polyvinyl acetate emulsion 5 Water The base wasdried and exposed to light under a translucent original. The exposedpaper was developed by passing it through a heated chamber havingtemperatures 121-177 C. A black dye image of good density and brightnesswas formed in the image areas of the heat developed print. The dyedensity and rate of development were better than that obtained withoutthe use of either dicyan- 7 diarnide or sodium trichloroacetate in thesensitizing solution.

Variations and modifications can be made in the procedures, compositionsand materials herein described without departing from the scope andspirit of the invention.

We claim:

1. Two-component diazotype photoprinting material susceptible todevelopment on heating, having on a surface of a supporting sheet, alight sensitive layer comprising an azo coupling component, alight-sensitive diazonium compound an acid stabilizer against prematuredevelopment and at least one amidine compound selected from the groupconsisting of acetamidine, propionami-de, butyramidine, dicyandiamidine,guanyl thiou-rea and salts thereof.

2. The article of claim 1 wherein said amidine compound comprises from 3to 40% by weight of the components of said light-sensitive layer.

3. The article of claim 1 wherein said amidine compound comprises from 1to 25 parts by weight per part by weight of diazonium compound.

4. The article of claim 3 wherein said amidine compound comprisesdicyandiarnidine.

5. The article of claim 3 wherein said amidine compound comprisesacctamidine.

6. A sensitizing composition for two-component diazotype printingmaterial susceptible to development on heating, comprising an aqueousmedium, an azo coupling component, light-sensitive diazonium compound,an acid stabilizer against premature development and at least oneamidine compound selected from the group consisting of acetamidine,propionamidine, butyramidine, dicyandiamidine, guanyl thiourea and saltsthereof.

7. The composition of claim 6 wherein said amidine compound comprisesfrom 1 to 15% by weight of said sensitizing composition.

8. The composition of claim 6 wherein said amidine compound comprisesfrom 1 to 25 parts by Weight per part by Weight of diazonium compound.

9. The composition of claim 8 wherein said amidine compound comprisesacetamidine.

10. The composition of claim 8 wherein said amidine compound comprisesdicyandiamidine.

11. Two-component diazotype printing material having on a surface of asupport sheet of cellulosic material, a light-sensitive layer comprisingan azo coupling component, light-sensitive diazonium compound an acidstabilizer against premature development and at least one amidinecompound selected from the group consisting of acetamidine,propionamidine, butyramicline, dicyandiamidine, guanyl thiourea andsalts thereof,

12. The article of claim 11 wherein said amidine compound compriscs from3 to 40% by weight of the components of said light-sensitive layer.

13. The article of claim 11 wherein said amidine compound comprises from1 to 25 parts by Weight per part by weight of diazonium compound.

14. The article of claim 13 wherein said amidine compound comprisesacetamidine.

15. The article of claim 13 wherein said amidine compound comprisesdicyandiamidine.

References Cited UNITED STATES PATENTS 2,545,423 2/1949 Duerr 96-753,153,592 10/1964 Klimskowski et a1. 96-91 X 3,157,503 11/1964 Kosar96-75 X 3,199,982 8/1965 Kashiwabara 96-75 X 3,255,007 6/1966 Kosar96-91 X 3,255,011 6/1966 Welch 96-75 3,271,155 9/1966 Aebi 96-753,316,092 4/ 1967 Klimkowski et al 96-75 FOREIGN PATENTS 1,249,91311/1960 France.

NORMAN G. TORCHIN, Primary Examiner.

C. L. BOWERS, Assistant Examiner.

